A first example of an imaging arrangement for use in this type of display is a barrier, for example with slits that are sized and positioned in relation to the underlying pixels of the display. In a two-view design, the viewer is able to perceive a 3D image if his/her head is at a fixed position. The barrier is positioned in front of the display panel and is designed so that light from the odd and even pixel columns is directed towards the left and right eye of the viewer, respectively.
A drawback of this type of two-view display design is that the viewer has to be at a fixed position, and can only move approximately 3 cm to the left or right. In a more preferred embodiment there are not two sub-pixel columns beneath each slit, but several. In this way, the viewer is allowed to move to the left and right and perceive a stereo image in his/her eyes all the time.
The barrier arrangement is simple to produce but is not light efficient. A preferred alternative is therefore to use a lens arrangement as the imaging arrangement. For example, an array of elongate lenticular elements can be provided extending parallel to one another and overlying the display pixel array, and the display pixels are observed through these lenticular elements.
The lenticular elements are provided as a sheet of elements, each of which comprises an elongate semi-cylindrical lens element. The lenticular elements extend in the column direction of the display panel, with each lenticular element overlying a respective group of two or more adjacent columns of display pixels.
In an arrangement in which, for example, each lenticule is associated with two columns of display pixels, the display pixels in each column provide a vertical slice of a respective two dimensional sub-image. The lenticular sheet directs these two slices and corresponding slices from the display pixel columns associated with the other lenticules, to the left and right eyes of a user positioned in front of the sheet, so that the user observes a single stereoscopic image. The sheet of lenticular elements thus provides a light output directing function.
In other arrangements, each lenticule is associated with a group of four or more adjacent display pixels in the row direction. Corresponding columns of display pixels in each group are arranged appropriately to provide a vertical slice from a respective two dimensional sub-image. As a user's head is moved from left to right, a series of successive, different, stereoscopic views are perceived creating, for example, a look-around impression.
Known autostereoscopic displays use liquid crystal displays to generate the image.
There is increasing interest in the use of emissive displays, such as electroluminescent displays, for example organic light emitting diode (OLED) displays, as these do not need polarizers, and potentially they should be able to offer increased efficiency since the pixels are turned off when not used to display an image, compared to LCD panels which use a continuously illuminated backlight.
There is also increasing interest in the use of reflective displays, such as electrophoretic displays and electrowetting displays.
This invention is based on the use, within an autostereoscopic display system, of a display arrangement that is emissive or reflective.
Emissive displays such as OLED displays and reflective displays such as electrophoretic displays differ significantly from LCD displays in how the light is emitted from the pixel. OLED pixels are emitters that emit light over a wide range of directions, and electrophoretic pixels are reflectors that reflect light over a wide range of directions. In the context of the present invention, such emitters and reflectors are also called diffuse emitters and diffuse reflectors, respectively. For a conventional (2D) display, OLED displays have a clear advantage over LCD displays that require a backlight and which, without taking special measures, emit light only in a narrow beam. However, the diffuse emission of the OLED material also poses a challenge as a lot of light is recycled inside the organic layers and is not emitted giving rise to a low efficiency. To improve, this various solutions have been sought to improve the out-coupling of the light out of the OLED.
However this improvement for 2D displays is in fact a problem for 3D autostereoscopic OLED displays. The solutions for increasing the light output cannot be used in autostereoscopic lenticular displays, as the light intended to be emitted from one lenticular lens may be reflected in the glass to a neighbouring lens. This reduces contrast and increases crosstalk.
Reflective displays such as electrophoretic and electrowetting displays may give rise to similar drawbacks as discussed above for emissive displays in the form of OLED displays.
Thus, there is a conflict between the desire for using emissive and reflective displays and the desire for low crosstalk within a 3D autostereoscopic display.